Experimental Study of the Combustion and Emission Characteristics of Lower Alcohols in a Constant Volume Vessel

Abstract

The synergistic effects of chain length, functional group position, and equivalence ratio on the combustion and emission characteristics of lower alcohols were investigated in a constant volume vessel at φ = 1.0, φ = 0.8, φ = 0.6, φ = 0.4, and P init = 1.87 MPa conditions in this work. The results indicated as follows. First, the most significant effect on autoignition temperature was the presence of branches in the hydroxyl group, followed by the number of carbon atoms, and then the methyl position in the carbon chain. Second, the combustion duration of branched chain alcohols was more sensitive to the equivalence ratio compared with that of straight chain alcohols. Third, methanol and 2-butanol had better combustion effects for stoichiometric combustion than thin combustion, while ethanol and isobutanol were more suitable for thin combustion. Finally, the total particle mass emissions and particle number concentration of all fuels were relatively low at φ = 0.6.

Comments on the Experimental Study of the Combustion and Emission Characteristics of Lower Alcohols in a Constant Volume Vessel

“…In the absence of such an error or an instrument malfunction, it would be difficult, if not impossible, to explain the source of additional energy required to achieve peak pressures measured. At other equivalence ratios, peak pressures reported by Shao et al display similar problems.…”

“…We show in the following paragraphs that the results presented in this paper are not correct and the conclusions reached are difficult to defend. We find it troubling that these results reported in the article by Shao et al, published in Energy & Fuels , should remain uncontested because they are seriously flawed.…”

“…The calculated maximum possible constant volume combustion pressures listed in Table are compared to those measured by Shao et al (Figure 5) in Figure for the stoichiometric conditions. Shao et al measured peak pressures in excess of what is thermodynamically possible (Figure ); for example, the measured pressure exceeds the maximum possible pressure by up to about 60% for methanol. It could be suspected that measuring peak pressures much higher than thermodynamically allowed could be an error in the pressure transducer calibration.…”

“…For the alcohols studied by Shao et al, the overall equilibrium reactions for an equivalence ratio of φ can be represented as where n is the number of carbon atoms in the alcohol molecule, X i represents the species in the combustion products, and N i is the corresponding number of moles of the product species. One can apply the first and second laws of thermodynamics to calculate the equilibrium temperature (and pressure for a constant volume case) for a given set of initial conditions and most abundant species in the products.…”

“…A recent publication in this journal reported results obtained from a series of measurements on a constant volume combustion chamber with premixed mixtures of lower alcohols, namely, methanol, ethanol, and three butanol isomers. Premixed alcohol–air mixtures used in the study covered an equivalence ratio range from 0.4 to stoichiometric.…”